The Chandley et al U.S. Pat. No. 4,589,466 issued May 20, 1986, illustrates the differential pressure, countergravity casting of molten metal wherein a gas permeable mold includes a crimpable metal fill tube sealingly connected to the lower end of a riser passage and adapted for immersion in an underlying molten metal pool during casting to fill a plurality of mold cavities in the mold. Once the mold cavities are filled with the molten metal by countergravity casting from the underlying melt, the metal fill tube is crimped closed while immersed in the molten metal pool to prevent molten metal run-out upon subsequent removal of the fill pipe from the molten metal pool. Molten metal remains and solidifies in the fill pipe above the crimped portion thereof as well as in the mold cavities, the intermediate riser passage and the ingates to each mold cavity. In the casting of higher melting point metals, the use of a crimpable metal fill pipe provides an unsatisfactory degree of reliability since the hot metal can occasionally melt through the fill pipe even when it is coated with a ceramic wash or layer. As a result, use of a metal fill pipe limits the type of metal that can be countergravity cast to those that will not melt through the fill pipe during the time that the metal remains molten therein. Moreover, crimping of the fill pipe is effected using a fluid cylinder driven crimping member and abutment which complicate operation of the casting apparatus. In addition, the crimped fill pipe is not reusable and must be discarded after use, increasing the cost of the casting process.
It is an object of the invention to provide an improved, economical, differential pressure, countergravity casting apparatus and method using a magnetically actuated valve means associated with the casting mold to prevent molten metal run-out from the mold when it is withdrawn from the underlying molten metal pool after filling the mold with molten metal.
It is another object of the invention to provide an improved, economical, differential pressure, countergravity casting apparatus and method using such a magnetically actuated valve means that permits the casting of higher melt point metals.
It is another object of the invention to provide an improved, economical, differential pressure, countergravity casting apparatus and method using such a magnetically actuated valve means that facilitates removal of pattern material, such as wax, from the mold prior to casting and facilitates filling of the mold with molten metal during casting.